Lung ventilators and control mechanism therefor



C. B. ANDREASEN LUNG VENTILATORS AND CONTROL MECHANISM THEREFOR Filed Dec. 5, 1958 2 Sheets-Sheet 1 INVENTOR Mag 6. 62am BY 4W1. M

ATTO R N EY LUNG VENTILATGRS AND CONTROL MECHANISM THEREFQR Christian B. Andreasen, New Hope, Pa, assignor to Air- Shields, Inc, Hathoro, Pa, a corporation of Delaware Filed Dec. 5, 1958, Ser. No. 778,390 16 Claims. ((1. 128-29) This invention relates to lung ventilating devices suitable for use with anesthesia machine systems and is more particularly directed to improvements in the control mechanism for changing the pressure phases of the entilating cycle including controls responsive to spontaneous respiration efiorts.

Lung ventilators of the type to which the present in vention is applicable are used to assist in the operation of breathing. Such machines normally have a breathing cycle which includes a positive pressure phase to assist inhalation and a negative phase to assist exhalation. Such ventilator devices are equipped with timing controls which regulate the period of the inhalation and exhalation phases. One of the objects of the present invention is to provide improved control mechanism with an additional control in the lung ventilator system which will switch the ventilator to the positive pressure phase immediately upon demand. Should the patient to which the equipment is attached initiate spontaneous respiration the resulting slight negative pressure developed in the system by the inhalation effort is utilized to immediately shift the ventilator to the positive pressure phase to assist the inhalation efiort.

Another object of the invention is to provide improved equipment of this nature which may be used either strictly as a time cycled unit or as a system in which the timed cycle may be interrupted by a spontaneous respiration effort.

Still another object involves the provision of improved timing device constuction with simplified valve control.

A further object of the invention is the provision of a lung ventilator drive system in which a source of gas under pressure provides the power for the drive of the ventilator to produce the positive and negative phases and at the same time this source of gas under pressure supplies the timing control to produce the change from positive to negative phase and vice versa. This object encompasses the provision of a valve controlled by a sensing diaphragm connected to the timing device to interrupt the normal timing function.

How these and other objects and advantages of the invention are accomplished will beclear from the following description of the drawing in which- FIGURE 1 is a diagrammatic view of the lung ventilating and control apparatus of the present invention.

FIGURE 2 shows the timing control unit with the mechanism in position to match the positive phase operation corresponding to the position of the ventilator parts in FIGURE 1.

FIGURE 3 shows the timing control unit with the timing mechanism shifted to a different position from that shown in FIGURE 1.

FIGURE 4 shows the manual valve in the connection between the spontaneous sensing valve and the timing device moved to closed position.

FIGURE 5 shows the manually controlled valve in the channel connection leading to the patient turned to manual position.

FIGURE 6 is a pressure diagram showing the relationship of pressure variation in various parts of the apparatus during operation.

Referring to the drawing FIGURE 1 shows a lung ventilating system in diagrammatic form. r A mask 5 or other suitable applicator means is provided for applying the Ventilating gas to the patient. Suitable valves are incorporated in the mask unit 6 so that the inhaled gas is supplied through the tube member 7. Exhaled gas is directed by means of the valving through tube 8 and through the cannister unit 9 for removal of the carbon dioxide. The remaining gas is then delivered back to the system through tube 10. A connecting tube 11 extends to the ventilator unit and connects to a valve 12 at its outlet 13.

' As will be clearly seen the valve 12 incorporates a movable valve portion '14 having a through channel 15 and a branch channel 16. In the position shown in FIGURE 1 the branch channel 16 is ineffective and the through channel 15 joins the outlet 13 with channel 17 leading to the ventilator apparatus. The ventilator 18 incorporates a distributor head 19 to which the channel 17 is connected. The distributor 19 is supported at the upper side of a transparent walled chamber 20 in which is mounted a flexible walled or bellows unit 21 which can expand and contract from the full line position 21 to the dotted line position 21a. The fully expanded position of unit 21 is controlled by a suitable stop 22. A valve 23 permits bleeding of air from the inside of the bellows unit 21 through valve 23 into the chamber 20 at any time the pressure is lower in chamber 20 than inside bellows unit 21.

Another bellows 24 is attached to the underside of the chamber 20, the inside of bellows 24 being connected to the chamber by means of aperture 25 in the bottom of chamber 20. Bellows 24 has a weighted bottom disk 26' to which is attached connecting rod 27. The bellows 24 can move from extended position where the bottom 26 is in full line position to compressed position such as shown by dotted outline 26a. Thus bellows 24 forms a variable volume chamber which serves to produce a variable pressure in the chamber 20. The external pressure from chamber 20 is in turn impressed on the bellows unit 21. On the expansion stroke of the bellows 24 the weighted bottom causes a negative pressure to be developed in the chamber 20 and this negative pressure is also transmitted through bellows 21 into the ventilating system.

, In order to control the magnitude of the positive or the negativepressurein the chamber 20 suitable relief valves are provided. Valve 28 permits bleeding of air from chamber- 20 at apredetermined pressure and thus limits the value of positive pressure which can be transmitted to the ventilator system through the bellows unit 21. Valve 28 is'adjustable by means of a spring 28a and a screw member 28b to vary the desired positive pressure setting within the limits suitable for operating the ventilating machine. Likewise the negative value of the pressure developed in chamber 24 can be controlled by valve 29 which permits entry of air th'roughthe valve upon reaching a predetermined difierential value. Likewise valve 29 may be adjusted to provide the desired magnitude of negative pressure. With this construction the pressures developed in chamber 20 may be applied through the bellows unit 21 to the breathing gas system without adrnitting any of the gas from chamber 20 into the breath ing gas. I

Suitable connecting channels are provided between the ventilator bellows unit 21 and the ventilator delivery channel 17. Channel 30 leads from bellows 21 to an outgoing branch channel 31 which is connected by a oneway valve 32 beyond'which a connecting channel 33 leads to channel 17. To transfer gas from the channel 17 ,to the bellows unit 21 it must pass from channel 17 through a channel 35, then through a one-way valve 36 after which itpasses through a branch channel 37 and channel 30 to the bellows unit 21; The flow directions in the various channelsare illustrated by means of suitable arrows it being noted that in certain sections such as atmosphere. v

; The upper side of the chamber 49 is formed by a fiexibly mounted wall 51. Above the wall 51 is another or less force, by means of an adjusting screw 65.

channel '17 and channel the flow may be in either di- 7 rection while in other sections such as channels 31 and 33 and channels 35 and 37 flow is in one directiononly 7 I to form a separate chamber above it. a

To actuate the bellows '24 to produce the positive and negative pressure phases in the system a cylinder 38 is,

27. "A gas supply tube 40 leads from the timing control device 41 to the cylinder 38. A supply of air or other gas under pressure (e.-g. 14 psi.) is delivered to the timer device 41 by means of a pipe. 42. By reference to FIG- URE 2. it will be seen that the gas supply to tube 40 is transmitted from a chamber 43 past a valve member 44 to a channel 45. The valve member 44 is held ofi its seat 46 (FIGURE 2) and up against seat 47 by means 'of a spring 48. Above the seat 47 there is another chamber 49 which connects by means of aperture 50 to the outside chamber 52 which connects to channels 53 and 54. Channel 54 connects'to the air' supply pipe 42 and incorporates a restricting orifice 55. Channel 54 extends to join the valve chamber 56, the lower surface of which is a. movable wall or diaphragm 57 which is attached to'a movable wallstructure 58 forming the upper surface of a control chamber'59. 'The area of the .Wall of chamber 59- is greater than that of the diaphragm57 of chamber 56 so thatwhen sufiicient pressure is'built up the. ,wa1l58 is moved upwardly and carries with it a rod .60 which lifts a valve member 61 off a seat 62. The valve 61 is norequipped with a piston39 attached to the connecting rod 'mally heldagainst the seat 62 by means of a valve spring overcome flw'pressure in chamber 56'and also produce sufficient'excess force to lift the valve .61 against the force 7 of spring 63. Spring 63 can be adjusted to apply more A chamber 66' above the valve 61 isconnected to the outer by means of a channel 67. Thus when valve 6-1 is opened channel 54 is relieved to atmospheric pressure. The actual loss of gas is small because the restricting orilice is quite small, the volumerequirement of the timer being low in comparison to the volume requirement for driving the ventilator. i

'As previously mentioned FIGURE- 1 Sh w's thepiston '39 and bellows 34 near the beginning of ther -positive pres-sure phase. As will be seen from'thepositionof the parts. in the timer 41, FIGURE, 2, both the flexible wall 51'and the. movable Wall 58 are in their. upper positions in which he upper valve 61 is open'fto relieve the pressure to atmospheric. Because the pressure in channel 54. and chamber 52 is atmospheric the valve member 44 admits gasunder pressure from the supply pipe 42 to the tube 4.0.

and thence, to the cylinder 38. to actuate the bellows 24 during 7 its pressure phase 'movement. To initiate, this positive'ptessure phase the pressure in chamber 59 had built'up by'virtue. of the bleeding of supply into chamher by way of a needle valve 68 and an orifice 69. Ilhe'necdle valve position is controlled by the knob 70 to increase or decrease the size of orifice 69 and thus the how rate from thechannel 53 to the chamber 59 to give the desired lengthvof time for pressure build up in chamber 59. 'Whenthe pressurehas built up in chamber 59 to. an amount somewhat below l-ine pressure it causes the 'wall 58: to move upWardlyand overcome the spring load 63 to open the valve 61 and release the pressure in channels 5 3 and 54 and chambers 52 and 56 to atmospheric. Releasing the pressure in chamber. 52 causes the movable Wall 51 and the attached rod'51a' tomoveupwardly to permit the valve member 44 to raise from theseat 46 and allowthe passage of the pressurized gas into the tube 40.

I This timer valve condition exists at the beginning of the pressure stroke of cylinder 38 and continues during this phase. Since channels 53 and 54 are at atmospheric the; pressure which has built upin chamber 59 causes I reverse flow from the chamber 59; through orifice 69 into the channels 53' and 54 and through valve 61 to the atmosphere. This bleeding of air from chamber 59 continues until the pressure in 59 has lowered sufiiciently so thatthe spring load 63 acting through the valve member 61 r and the rod 60 causes the moving wall 58 to be pushed spring 48 and. cause it to seat against the lower seat 46. t

In this position the upper orifice 47 is opened to the channelAS and the pressure supply is cut off from the cylinder 38. Exhaust from the cylinder- 38 may take place to'the atmosphere by way of tube 40, channel 45, orifice 4'7, chamber 49 and orifice 50. This is the'posi tion of the parts of the timer during thenegative phase operation of the timer during which time the weight of the bellows disk 26 causes the piston 3-9 to move-downwardly in the cylinder '38fand causes the air to exhaust from the cylinder through the "tube 40 and out to the atmosphere as noted; v

During this negative phase operation there is from" channel 53 which is now at line pressure into the chamber 59 past the needle valve 68. Flow in this direction gradually builds up the pressure in the chamber 59. 'When the pressure again reaches the critical point it causes movement of the Wall 58 and opening of the valve V6} to relieve the pressure in the timer channels 53 and 54 and permit shifting ofthe lower valve 44 to. the up position to initiate another positive phase of the cycle. By changing the pressure on spring 63 by" means of the adjusting screw 65 the length of the negative phase can be, changed I with respect to the length of the positive phase. By

adjusting the needle valve 68 through rotation of the knob I 76 the time for increase and decrease of the. pressure'in chamber 59 may be adjusted to increase or decrease the length of the" complete cycle. Thus by thesetwo adjust- I ments the cycle length may be changed or the phase rela- 1 tionship of'the cycle maybe-varied While retaining the cycle time constant. a t

' Referring again to FIGURES 1 and 2 it will be' seen that a tube 71' connects the control device 41 with the distributor unit 19 ofthe ventilator device. Tube 71 connects into channel 54 of the time device. A'valve 7 2 having an internal member 73 permits closing the line 71 I so that the connection between the'timer 'device 41 and V the ventilator is eliminated. The closed position of the valve 72 is shown in FIGURE4 while FIGURE 1 shows A the movable member 73 of the valve 72in open post-1 tion. I p v a In the distributor unit 19 channel 74 connects to the tube 71 and extends to an outlet 75. The outletfof'chan nel 74 normally opens into a small'charnber-76 which is connected. by channelj77 to the'outsideatmosphere. ,ZA

the anesthesia machine channel 171' Thus the lower chamber 79 is in direct. connection with the bellows unit '21; While the upper chamber 80' is separated from the bellows 21 by the one-way valves 32 and 36. w

A small projection 84 is supported on the lower side of the wall 81 in position to hold flexible'wall 78; against the 7 outlet of channel 74 to block it. -Dl11ti'ng the negativ phase there is a slight pressure differential dueto. the j loss past valve 36. The slightly lower absolute pressure,

in bellows 2-1 causes wall 81 to be held in closed position. During the positive phase there is also a pressure difference between bellows unit 21 and channel 17 to cause flow past valve 32. This slight increase in pressure in chamber 79 causes opening of outlet 75 but under this condition timer valve 61 is also open. Inspiration continues until both outlet 75 and valve 61 are closed. The negative phase begins when flow past valve 32 ceases. During the negative phase of operation the downward motion of bellows 24 develops the negative pressure in the chamber 24 which is transmitted by the bellows unit 21 and through its expansion the negative pressure causes flow from the patients lungs through the channel 17, the channel 35, past the valve 36 and through channel 37 to the bellows unit 21.

If during this negative pressure phase the patient attempts spontaneous inspiration, this causes in the channel '17 a negative pressure slightly greater in negative value than that being produced by the bellows 21. The inside of bellows 32a above valve 32 is connected by channels 77a and 77 to atmospheric pressure. Thus a negative pressure developed in channel 17 cannot open valve 32. As a result the greater negative pressure, that is, the lower absolute pressure in channel 17 produces a sufiicient difierential between chambers 7 and 89 so that the wall 81 is lifted to remove member 84 from flexible wall 7%. This allows channel 74 to be opened through channel 77 to atmospheric pressure. This has the immediate efiect of reducing the pressure in the timing device channels 53 and 54 to atmospheric with the result that both the lower valve 44 and the upper valve 61 move to their upper positions. Gas under pressure flows into the line 49 and causes the cylinder 33 to initiate a positive pressure stroke of the ventilator. Thus the ventilator responds immediately to the patients effort and produces a positive pressure to assist the spontaneous inspiration. When the cycle is changed by the patients inspiration the gas under pressure in chambers 52 and 56 is exhausted to atomsphere through channel 77 in a fashion which gives an audible indication that the patient has initiated the cycle. The positive pressure phase continues until the timer unit valve 61 and the outlet 75 have closed to demand the negative phase.

A separate channel 85 is provided leading to the ventilator channel 31. Channel 85 connects through the valve 12 by means of a tube 86 with suitable sources of supply, illustrated at 87 and S8, of breathing gas which may include an anesthesia gas and oxygen or additional gases when desired. Flowing the breathing gas at a point between bellows unit 21 and valve 32 prevents loss of sensitivity to the efiort of the patient to inspire and thus improves the response of the apparatus.

It will be noted that when the valve 12 is in the position shown in FIGURE 1 the breathing gas is connected to the channel 85 through the valve channel 89. However when the valve 12 is rotated to the position shown in FTGURE 5 the connection to the mechanical ventilator machine is shut off and the valve channel 16 connects the breathing bag 91 to the patient. In this position a valve channel 90 connects the breathing gas supply with the delivery channel 15, 16. Thus the system can be switched from automatic operation to manual when desired.

Another improvement in the ventilator apparatus is shown in FIGURE 1 where a special relief valve device is connected with the variable pressure chamber 2% An outlet orifice 92 is provided with a one-way valve member 93 which is held down by spring 94 reacting against a flange 95 which engages the valve member 93. The valve chamber above valve member Q3 is open to the outside atmosphere.

Connected to tube 71 from the timer 41 is a tube as leading to chamber 97 in which is mounted a piston 93. Piston rod 99 connects piston 98 with the flange 5. The portion of chamber 97 above piston 93 is open to the atmosphere.

From the previous description of the timer operation the pressure in channel 54 and thus tube 71 is released to atmospheric during the positive pressure phase of the ventilating cycle. As a result the pressure both above and below piston 93 is atmospheric so that the spring 94 is effective in holding the valve member 93 on its seat. Upon closing of the timer valve 61 at the end of the positive pressure phase the pressure in channels 71, 96 and chamber 97 causes the piston 98 to rise thus leaving the valve member 93 free to open in response to pressure above atmospheric in chamber 29. Thus for a brief instant at the end of the positive pressure phase some of the gas from chamber 2-1"; can escape through valve 93. Escape in this fashion lasts only until the bellows 24 has moved sufficiently to create a negative pressure in chamber 2% Escape of this gas to the atmosphere has the efiect of bringing the negative phase more quickly because less stroke is required to change the compressed gas in chamber 2% to expanded gas. The bleeding of gas hrough valve $8 gives an effective increase in capacity for the bellows 2 during the negative phase. This valve also provides an improved method of bleeding 01f excess gas fed to the ventilator system and which overflows to chamber 29 from bellows unit 21 by way of the overflow valve 23. If desired to shut off this auxiliary bleeder valve system the shut-off valve 72 may be located in tube 71 at a point between connecting tube t; and the timer 41.

The general pressure relationships are illustrated in the diagram in FIGURE 6 although the relative pressure values shown are not necessarily to scale. Atmospheric pressure is represented by P0 while the pressure of the supply line 42 is Ps. Solid line P54 is the pressure curve for channel 54 which is the same pressure as valve chambers 52 and 56. Dash line P40 represents the pressure in the tube 41 leading to the drive cylinder 38. Broken line P59 shows the variation of pressure in the control chamber 59 of the timer and varies from a value PL to a higher value PH. These values may be varied by adjusting spring 63. The dotted line P21 represents the pressure in the ventilatorsystem as transmitted by bellows unit 21.

Thus at point A of the diagram a negative pressure phase is beginning. Full line pressure Ps is applied to the timer since upper valve 61 is closed. This results in lower valve 44 closing ofl. line pressure to the drive with the result that tube 40 is exhausting to atmospheric pressure, P0. This allows the drive bellows 24 to be expanding and thus causing a negative pressure in bellows 21 as shown by dotted line P21 which is below atmospheric pressure. During the time interval from A to B the pressure in control chamber 59 is gradually increasing as shown by P59.

When the pressure P59 reaches PH value the valve 61 opens. Thus at position B, FIGURE 6, the pressure in channel 54 falls to atmospheric P0 with the result that lower valve 44 opens to admit pressure to tube 40. Thus the value of P40 immediately increases to Ps and the piston 39 causes a pressure phase to develop in bellows unit 21. Thus between B and C curve P21 is at a positive pressure, this being the pressure phase of the cycle. During this period from B to C the chamber pressure P59 reduces till it reaches pressure PL when valve 61 again closes to start another negativepressure phase.

The vertical portions of curves P54 and P40 are shown slightly displaced .for clarity. Actually these lines should be superimposed.

From the foregoing it will be evident that I have provided an improved lung ventilator control. The arrangement of valves provides a simple and reliable control for applying and shutting oh? the ventilator driving energy. The use of a valve having a double seat and double function, combined with a pressure control to shut ofi" flow of gas under pressure, helps to give improved the quality and efficiency of operation. -Delivery of the breathing gas into the system between the bellows unit and the one-way valve gives adequate sensitivity to assure reliable spontaneous respiration control.

I claim: i

1. Lung ventilating apparatus having a delivery system for supplying breathing gas to a patient, pressure applying means for applying alternate'positive and negative pressure phases to the system, a controller having a con nection to said pressure applying means for changing the phase from positive to negative and vice versa, said controller having a supply of pressure gas thereto for actuating purposes, a valve in said controller to release the controller pressure to atmospheric during the positive.

phase of operation of the ventilating apparatus, an auxiliary control for causing a change from negative to positive pressure application in response to a negative pressure induced in the delivery system by attempted spontaneous respiration on the part of the patient, said auxiliary control including a pressure responsive member and a valve, said pressure responsive member being connected to said delivery system and said valve having a connection to said controller, and a connection to the atmosphere to permit release of the controller pressure to atmospheric in response to'spontaneous inhalation.

2. Lung ventilating apparatus constructed in accordance with claim 1 in which a shut oil valve is provided in the connection between the auxiliary control and the controller to'allow operation either as a direct pressure applied ventilator or as an assister ventilator responsive to spontaneous respiration pressures. v a

3. Lung ventilating apparatus including'a breathing gas conveying system, a pressure varying container connected said variable pressure chamber from a positive pressure to a negative pressure and vice versa, said timing device being connected with a supply of gas under constant pressure, interconnecting means between said timing de- '-vice and said variable pressure chamber, said means in-f eluding a channel leading from said timing device, a first valve mounted in said timing device to intermittently" permit flow of gas out of said device through said channel leading therefrom and then close off the flow, bias means urging said valve to gas flow position, a pressure responsive wall in said timing device having a member engageable with said valve to move it against said bias means to close off the flow, a second valve in said timing device having internal connections to control said first va1ve,a' control chamber having a movable wall with a connection to said second valve to control its movements, a channel leading from said second valve to the atmosphere,

opening of said second valve causing release of pressure on said pressure responsive wall to permit opening of said first valve to allow flowof gas through said channel leading. from said timingdevice and closing of said second valve causing pressure build up at said pressure respon'sive Wall to close said first valve against flow of said pressure gas.

5. Lung ventilating apparatus having a variable pressure chamber, a. flexible Walled container supported in said chamber, an applicator for administering breathing gas to a patient, a breathing gas conveying system between said container and said applicator, said system including a portion adjacent said container having two branch channels, a one-way valve mounted in each of to one end of said system,-a portion of said system adjacent said container having a branch channel with a oneway valve for conveying gas moving from said container and another branch channel with a one-way valve for conveying gas moving to said container, a main channel in said system to which said branch channels connect, a timing device having operative connections to said container for controlling the application of negative and positive pressure and thus the direction of flow to and from said container, said timing device being actuated by a. pressure gas supply thereto, a control valve in said timing device movable to release the gas in said timing device to atmospheric pressure,,means responsive to the change to atmospheric to induce a positive pressure apsaid branch channels, a main channel into which. said I connecting channelextending from one of said. branch channels at a point between said container and one of said one-way valves to one side of. said diaphragm wall, another connecting channel extending from the said main channel to the other side of said diaphragm wall, a timing device operated by gas pressure, said timing device having operative connections to said variable pressure chamber for controlling the change of pressure in the chamber,

plieation to the breathing gas system, an auxiliary ccntrol for said'timing device including a pressure actuated 7 wall member, a channel leading to one side of said wall member from one of said-branch channels at apoint between'said container and said one Way valve, a connection from the other'side of "said Wall member to said 7 main channel, a valve, device operated by said pressure actuated member, and a connection from said timing de- 'vice to the atmosphere controlled by said valve device thereby causing said timing device to'induce a positive pressure application to the breathing gas's'ystem in re spouse to a negative pressure applied to said pressure a valve in said timing device to release the gas pressure channel connection.

6. Lung ventilating apparatus having mechanism actuated by a supplyof gas under pressure, a timing devicef to control admission of gas to the actuating mechanism and release of gas therefrom, said .device having. a channel connecting it to said actuating mechanism, a valve member 1n said device, blas means normally urging said valve member to gas admission position, a pressure actuated diaphragm having a connection to said valve member to move it against said bias means to shut oil gas flow to said actuating mechanism, said timing deviceincluding a second valve opening to atmosphere, said second valve havingmeans to normally urge it to closed position, a control chamber having a movable wall with a connection to actuate said second valve, a channel structure in said timing. device having a restrictive orifice connecting it to said source of pressure gas, said channel structure having connections to said diaphragnnsaid second valve and said control chamber, the connection to said control chamber in said channel structure to permit opening'of said first valve to admit pressure gas to said actuating mechanism, release of pressure in said channel structure also permitting flow of gas from said control chamber to cause gradual pressure reduction, changing the adjustment of the restrictive orifice causing variation in the timing of the lung ventilating actuating mechanism.

7. Lung'ventilating apparatus in accordance with claim 6 in which said actuating mechanism incorporates a channel connected to said channel structure in said timing device, said channel extending to the atmosphere, a third control valve connected to said channel to control opening and closing it to atmosphere, said third valve having control means connected to the lung ventilating ap paratus, said control means being actuated under the influence of negative pressures induced by inhalation effort of a patient.

8. Lung ventilating apparatus having a variable pressure chamber, powered mechanism connected to said variable pressure chamber to produce a positive pressure phase therein and a negative pressure phase, a separate chamber having a flexible wall mounted in said variable pressure chamber, a breathing gas applicator, connecting means leading from said separate chamber to said applicator, said connecting means incorporating a main conducting channel and two short connecting channels, a one-way valve mounted in each of said connecting channels, one of said connecting channels and its one-way valve providing for flow from said separate chamber to said main channel, the other of said connecting channels and its oneway valve providing for flow from said main channel to said separate chamber, a pair of chambers separated by a flexible diaphragm, a channel leading from said separate chamber to one side of said diaphragm, another channel connecting the other side of said diaphragm to said main channel, a timing device having a connection to said powered mechanism and having a control therein operable to change the variable pressure chamber from negative pressure to positive pressure, said control having means responding to release of gas pressure to atmospheric pressure to initiate a positive pressure phase, a gas flow channel extending fiom said timing device to the atmosphere, a shut-oif control in said gas flow channel having an operating connection to said diaphragm, said diaphragm being movable by differential pressure thereon to cause said shut-off control to open said channel to atmospheric thereby actuating said timing device to initiate a positive pressure phase.

9. Lung ventilating apparatus having a channel system for delivering breathing gas to a patient, a flexible walled chamber connected to said channel system, equipment having operative connections with said flexible walled chamber for alternating the pressure in said flexible walled chamber from a pressure above atmospheric to a pressure below atmospheric, a timing control device for said equipment, said device having a supply line connected to it for delivering gas under pressure, a delivery line leading from said device to said equipment, a channel in said device connected to said delivery line, said channel having a first opening to connect it to said delivery line, said channel having a second opening to connect it to the outside of said device, a valve member located in said channel having bias means to move it to block the second of said openings during above atmospheric operation, and a pressure actuated diaphragm having means engageable with said valve member to move it against said bias means to block the first of said openings during the period of operation below atmospheric pressure.

10. A timing control device for a lung ventilator to control the periodic delivery of gas under pressure to the ventilator and the release of gas therefrom, said device having a supply line connected to it for delivering gas under pressure, a delivery line attached to and leading from said device, a channel in said device connected to said delivery line, a first opening between said supply line and said channel, a second opening between said channel it) andthe outside atmosphere, a valve member having a spring to move itto block said second opening, a movable wall supported adjacent said second opening and having a part engageable with said valve to move it to block said first opening, a control chamber in said timing device having a connection with said movable wall, a channel in said timing device extending between said control chamber and said supply line, said channel having a restrictive orifice therein, a relief valve assembly in said timing device having a connection to said control chamber channel, said valve assembly having an operative connection with said control chamber and being movable thereby to open position to connect said last mentioned channel to atmosphere. I

ll. Lung ventilating apparatus having a delivery system for supplying breathing gas to a patient, a pressure varying chamber connected to said system, said system having a main delivery channel, a branch channel extending between said chamber and said main channel and having a one-way valve to allow flow from said main channel to said chamber, a second branch channel extending between said chamber and said main channel and having a oneway valve to allow flow only from said chamber to said main channel, said last mentioned one-way valve having a flexible walled structure connected thereto to form a small chamber, a vent connecting said small chamber to the outside atmosphere, a timing control device having operative connections to change the pressure in said pressure varying chamber from a positive pressure phase to a negative pressure phase and vice Versa, a movable wall member in said apparatus, a chamber on each side of said wall member, a connecting passage from the chamber on one side of said wall member to the first branch channel leading to said pressure varying chamber, a connecting passage from the chamber on the other side of said movable wall member leading to said main channel, said timing control device having a venting valve therein which when opened causes initiation of a positive pressure phase to said pressure varying chamber, a connecting line ex tending from said timing control device to a point adjacent said movable wall member and means actuable by said movable wall member to control the venting of said connecting line to atmospheric thereby providing an alternate means for initiating a positive pressure phase to said pressure varying chamber.

12. Lung ventilating apparatus having a variable pressure chamber, a flexible walled chamber mounted inside said variable pressure chamber, a breathing gas system connected to said flexible walled chamber, pressure varying means connected to said variable pressure chamber to provide a positive pressure phase and a negative pressure phase, a timing control device connected to said pressure varying means, said timing device having a connection to a source of pressurized gas, an internal control channel in said timing device having valve means to open said channel to atmosphere, closing of said valve means causing a pressure increase above atmospheric in said internal control channel, said pressure varying means having operative connections to induce negative pressure in said variable pressure chamber when said valve means is closed, and a relief valve device connected to said variable pressure chamber having a valve member and a pressure actuated valve controlhaving a channel connection to the internal control channel of said timing control device.

13. Lung ventilating apparatus in accordance with claim 12 in which said relief valve device incorporates a spring which holds said valve member closed when positive pressure is present in said variable pressure chamber and a piston releases the spring pressure when the phase changes to the negative phase thereby permitting momentary release of gas during the change from positive to negative pressure in said variable pressure chamber.

l4. Lung ventilating apparatus having a variable pressure chamber, a channel system for delivering breathing gas connected to said chamber, said system including a main delivery channel and a plurality of one-way valves located between said chamber and said main channel, control equipment connected to said variable pressure cha1n- 1 her to vary the pressure in said chamber including a de vice for producing a timed cycle, means for supplying pres-- sure gas to said device and valve means to release gas pressure in said device to atmospheric, an auxiliary control for interrupting a timed cycle'in response to induced pressures in said main channel, said auxiliary. control having a control channel connected into said device for producing a timed cycle and leading to the-atmosphere, a pressure responsive member in said auxiliary control, a control channel therefor leading from said main channel, to said auxiliary control, meansattached to said pressure responsive member to open and close said control channel leading from said timed cycle device to the atmosphere.

15, Lung ventilating apparatus having a variable pressure chamber, a channel system for delivering breathing gas connected to said chamber, said system having a main livery channel, a' relief channel leading from said control device, means movable by said movable Wall to open and,

a close said relief channel and a connection for conveying 1 breathing gas into said channel system, said connection en- V livery channel by said one-way valvesi a 16. Lung ventilating apparatus in accordance with claim operable breathing bag.

1 2 movable wall having one side connected to said main detering said system at a point separated from said main 'de 15 inwhich said main channel includes a switching valve, a manually operable br'eathing'bag connectible through said switching valve, said connection for conveying breathing" gas extending through said switching valve, said switching valve including a control channel to direct said connection for breathing gas into said main channel when said switching valve is moved to connect the manually References Cited in the file of this patent UNITED STATES PATENTS 2,547,458 Goodner Apr. 3,1951 2,591,120 -Blease Apr. 1, 1952' 2,737,178 Fox Mar.,6, 1956 2,867,210 Bennett Jan. 6, 1959' 2,904,035 Andreasen Sept. 15, 1959 'FOREIGN PATENTS 1,017,808

France Oct. 1, 1952'" 

